C. Adloff et al., MULTIPLICITY STRUCTURE OF THE HADRONIC FINAL-STATE IN DIFFRACTIVE DEEP-INELASTIC SCATTERING AT HERA, The European Physical Journal. C: Particles and Fields, 5(3), 1998, pp. 439-452
The multiplicity structure of the hadronic system X produced in deep-i
nelastic processes at HERA of the type ep --> eXY, where Y is a hadron
ic system with mass M-Y < 1.6 GeV and where the squared momentum trans
fer at the pY vertex, t, is limited to \t\ < 1 GeV2, is studied as a f
unction of the invariant mass M-X of the system X. Results are present
ed on multiplicity distributions and multiplicity moments, rapidity sp
ectra and forward-backward correlations in the centre-of-mass system o
f X. The data are compared to results in e+e- annihilation, fixed-targ
et lepton-nucleon collisions, hadro-produced diffractive final states
and to non-diffractive hadron-hadron collisions. The comparison sugges
ts a production mechanism of virtual photon dissociation which involve
s a mixture of partonic states and a significant gluon content. The da
ta are well described by a model, based on a QCD-Regge analysis of the
diffractive structure function, which assumes a large hard gluonic co
mponent of the colourless exchange at low Q2. A model with soft colour
interactions is also successful.